Project Summary Knee osteoarthritis (OA) is one of the most common health problems and a leading cause of disability among veterans. Physical therapy (PT) and ongoing exercise are associated with reduced pain and improved physical function among patients with knee OA, yet the majority of veterans with OA are physically inactive. Furthermore, PT services are a limited resource in the VA health care system, with demand exceeding supply. VA patients with knee OA generally receive only one or two PT visits. Prior research indicates this amount of clinical contact time is not sufficient to provide patients with the assessment, instruction, and support needed to adopt and maintain an exercise program, particularly in the context of a chronic pain condition. Therefore development, testing, and implementation of mechanisms to cost-effectively expand PT services for knee OA may play a key role in improving pain and other outcomes in this large group of veterans. This research examines a group-based approach to delivering PT for knee OA, which can extend services to more veterans, for a greater number of sessions per veteran, at lower staffing costs. The objective of this study is to compare the effectiveness of a group-based PT program for knee OA with usual individual PT care for knee OA. This study will be a randomized controlled trial of a 12-week, group-based PT program among N=376 veterans with symptomatic knee OA at the Durham VAMC. Participants will be randomly assigned to the group-based PT program or individual PT (usual care). The group PT arm will include 6 1 to 1 1/2 hour visits (every other week) led by a physical therapist and exercise physiologist, with 8 participants per group. The individual PT arm, modeled after typical PT care for knee OA at the Durham VAMC and other health care settings, will include 2 1-hour visits with a physical therapist, 2-3 weeks apart. The group PT sessions will include group instruction in joint care (activity pacing and joint projection), group discussion of exercise successes and barriers, group exercise, and scheduled individual consultations with the physical therapist (2 per participant, 15-20 minutes each) to address specific functional and therapeutic needs. While the individual PT sessions will differ in structure, they will include the same informational, assessment, and therapeutic content as the group sessions. Both groups will be given instructions for the same home exercise program. The primary outcome for this study will be the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC). The secondary outcome will be objectively assessed physical function (Short Physical Performance Test Protocol). These outcomes will be assessed at baseline and 12-week follow-up. The WOMAC will also be assessed via telephone at 24-week follow-up to examine whether any observed intervention effects are maintained. Mixed linear models will be used to compare outcomes for the two study arms. We will also conduct an economic analysis of the group-based PT program.